Irregular-shank tools and drivers therefor

ABSTRACT

A tool ( 1 ) has a distal operative portion and a proximal shank ( 2 ) with a mounting portion ( 3 ), for mounting the tool in a holder ( 10 ). A substantial portion of the mounting portion has a cross-sectional shape with at least one and fewer than six 60-degree segments thereof having segment ends joined by a flat surface ( 5 ). The holder has a distal axial aperture or mounting hole ( 12 ) for receiving the tool ( 1 ), the aperture having a cross-sectional shape which has 60-degree segments thereof having segment ends joined by a flat surface ( 13 ), but no more such flat surface segments than those corresponding to flat surface segments of the tool. The holder further has a ball-detent ( 21 ) mechanism or other locking mechanism for engaging the mounting portion ( 3 ) of the tool ( 1 ).

TECHNICAL FIELD

This invention relates to tools such as drill bits, screwdriver bits,reamers, router bits, grinding wheels, spade bits, countersinks,mandrels, polishing tools, wheel brushes, wheel cutters and other toolaccessories, and to driving tools for same, for example a drill or ascrewdriver. In particular, the invention relates to tool configurationswhere the tool shanks have certain irregular (i.e. non-circular) shapesadapted to fit cooperative holder portions of the bit-driving tools.

DISCLOSURE OF INVENTION

It is an object of the invention to provide novel tools, and novelholders for those tools for mounting on or incorporation in a drivingimplement, such as a hand tool or a power tool, the holder having amounting hole and a retaining/locking mechanism which accepts andsecurely holds a variety of tool shank mounting portions of differentshapes. In the preferred embodiment of the tools, their cross-sectionshave at least one flat portion across at least a 60 degree segment ofthe tool shank, to provide sufficient torque transfer between the holderand the tool. The holder mounting hole has a number of flats rangingfrom one to five corresponding to the number of flat portions on themounting portion of the tool, the flat sections of the hole being tiedtogether by substantially circular sections. A holder according to theinvention can securely mount and hold not only tools having mountingportions according to the invention, but also standard hex tool bits,such as drill bits and screwdriver bits.

In the invention, the tool has a distal operative portion and proximalshank with a mounting portion, for mounting the tool in the holderportion of the driving tool. A substantial portion of the mountingportion has a cross-sectional shape with at least one and fewer than six60-degree segments thereof having segment ends joined by a flat surface.The holder has a distal axial aperture or mounting hole for receivingthe tool, the aperture having a cross-sectional shape which has60-degree segments thereof having segment ends joined by a flat surface,but no more such flat surface segments than those corresponding to flatsurface segments of the tool.

In an alternative embodiment of the tool, the mounting portion thereofhas a cross-sectional shape with at least one protrusion therefrom,adapted for engagement in at least one slot in aperture of the holder,or has at least one slot therein, adapted for engagement with at leastone radially-inward protrusion in the aperture.

The invention encompasses not merely the tools, but also the tools andholders in combination.

The holder has locking means for engaging the mounting portion of thetool. The locking means either comprises manually operated engagementmeans for locking the mounting portion in the holder, for manuallyengaging the engagement means in a locking position after insertion of atool in the holder, or automatically operated engagement means forlocking the mounting portion in the holder, the engagement meansautomatically engaging in a locking position around the tool when thetool is inserted into the holder.

In a preferred embodiment, the tool has two said 60-degree segmentshaving segment ends joined by a flat surface, the two segments being onopposite sides of the tool from each other.

Advantageously, a portion of the mounting portion has a circumferentialgroove extending at least partway around the mounting portion'scircumference, adapted to receive locking means of a holder of abit-driving tool, such as a locking ball of a ball-detent mechanism. Thegroove may extend completely around the circumference, or may be only inat least one of the flat surfaces. Alternatively, the groove may be in asurface of the mounting portion other than any of the flat surfaces. Anysuitable ball-detent mechanism, combination ball detent and transitionball mechanism, or any other suitable locking means may be used,including some locking means perhaps not presently known. Non-limitedexamples of such locking means may be seen, for example, in U.S. Pat.Nos. 6,199,872, 5,470,180, 5,682,800 and 5,779,404, and in publishedinternational patent application no. PCT/CA00/00521. Thus it should beclearly appreciated that the invention resides in the novel tools, andin the combination of the tools and appropriate holders, rather than inthe holders themselves.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be more clearly understood, preferredembodiments thereof will now be described in detail by way of example,with reference to the accompanying drawings, in which:

FIG. 1A is an end view of a first embodiment of a tool having a mountingportion of a shank according to the invention,

FIG. 1B is a side view of the tool of FIG. 1A,

FIG. 2A is an end view of a second embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 2B is a side view of the tool of FIG. 2A,

FIG. 3A is an end view of a third embodiment of a tool having a mountingportion of a shank according to the invention,

FIG. 3B is a side view of the tool of FIG. 3A,

FIG. 4A is an end view of a fourth embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 4B is a side view of the tool of FIG. 4A,

FIG. 5A is an end view of a fifth embodiment of a tool having a mountingportion of a shank according to the invention,

FIG. 5B is a side view of the tool of FIG. 5A,

FIG. 6A is an end view of a sixth embodiment of a tool having a mountingportion of a shank according to the invention,

FIG. 6B is a side view of the tool of FIG. 6A,

FIG. 7A is an end view of a seventh embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 7B is a side view of the tool of FIG. 7A,

FIG. 8A is an end view of an eighth embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 8B is a side view of the tool of FIG. 8A,

FIG. 8C is an end view of a variation of the tool of FIG. 8A,

FIG. 8D is a side view of the tool of FIG. 8C,

FIG. 9A is an end view of a ninth embodiment of a tool having a mountingportion of a shank according to the invention,

FIG. 9B is a side view of the tool of FIG. 9A,

FIG. 10A is a sectioned side view of a first embodiment of a holderaccording to the invention,

FIG. 10B is an end view of the holder of FIG. 10A,

FIG. 11A is a partially sectioned side view of a holder according to theinvention in position for receiving a tool of FIGS. 2A and 2B,

FIG. 11B is a partially sectioned side view of the holder and tool ofFIG. 11A, showing the mounted tool inside the holder,

FIG. 12A is a partially sectioned side view of a holder according to theinvention in position for receiving a standard hex cross-section tool ofknown art (a drill bit),

FIG. 12B is a partially sectioned side view of the holder and tool ofFIG. 12A, showing the mounted tool inside the holder,

FIG. 12C is an end view of the holder and tool of FIG. 12B as seen fromline A-A, showing the mounted tool inside the holder,

FIG. 12D is an end view of the axial opening of the holder,

FIG. 13A is a partially sectioned side view of a holder according to theinvention in position for receiving a further type of standard hexcross-section tool of known art (a screwdriver bit),

FIG. 13B is a partially sectioned side view of the holder and tool ofFIG. 13A, showing the mounted tool inside the holder,

FIG. 13C is an end view of the holder and tool of FIG. 13B as seen fromline B-B, showing the mounted tool inside the holder,

FIG. 14 is a perspective view of a mounting portion according to oneembodiment of the invention,

FIG. 15 is a perspective view of a mounting portion according to afurther embodiment of the invention,

FIG. 16A is a side view of a tenth embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 16B is an end view of the tool of FIG. 16A,

FIG. 17A is a side view of an eleventh embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 17B is an end view of the tool of FIG. 17A,

FIG. 18A is a side view of a twelfth embodiment of a tool having amounting portion of a shank according to the invention,

FIG. 18B is an end view of the tool of FIG. 18A,

FIG. 19A is a side view of a thirteenth embodiment of a tool having amounting portion of a shank according to the invention, and

FIG. 19B is an end view of the tool of FIG. 19A.

BEST MODES FOR CARRYING OUT THE INVENTION

FIGS. 1A to 9B show different embodiments of mounting portions of toolshanks according to the invention. The tool is shown as a drill bit, butany tool having a shank with a mounting portion can be used. Thus, anytools such as drill bits, screwdriver bits, reamers, router bits,grinding wheels, spade bits, countersinks, mandrels, polishing tools,wheel brushes, wheel cutters etc. are suitable for being provided withmounting portions according to the invention.

In FIGS. 1A and 1B a first embodiment of a mounting portion 3 of a shank2 of a tool 1 is shown. The shank is generally circular in cross-section7, and has one flat surface 5, which corresponds in width to a 60 degreesection of the shank. An optional retention groove 4 is arranged towardsthe outer end of the mounting portion, for cooperation with lockingmeans of a holder (described later).

A second embodiment of a mounting portion 3 of a shank 2 of a tool 1 isshown in FIGS. 2A and 2B. This is the embodiment presently preferred bythe applicants. It is very similar to the first embodiment, but has twoflat portions 5 arranged opposite each other on the shank. The shank isgenerally circular in cross-section 7. An optional retention groove 4 isarranged towards the outer end of the mounting portion.

A third embodiment of a mounting portion 3 of a shank 2 of a tool 1 isshown in FIGS. 3A and 3B. The shank is generally rectangular incross-section, having two first flat portions 5 arranged opposite eachother on the shank and two second generally flat portions 5′ connectingthe first flat portions. Each first flat portion 5 corresponds in widthto a 60 degree section of the shank. An optional retention groove 4 isarranged towards the outer end of the mounting portion.

FIGS. 4A and 4B show a fourth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section,with knurles/splines 6 arranged along at least a substantial portion ofthe mounting portion. The knurles/splines are arranged to cooperate withspecial tool holders having a correspondingly shaped hole, for enhancedtorque transfer between holder and tool. The shank has one flat surface5, which corresponds in width to a 60 degree section of the shank. Anoptional retention groove 4 is arranged towards the outer end of themounting portion.

FIGS. 5A and 5B show a fifth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section 7,with a keyway 6′ arranged along at least a substantial portion of themounting portion. The keyway is arranged to cooperate with special toolholders having a correspondingly shaped hole, for enhanced torquetransfer between holder and tool. The shank has one flat surface 5,which corresponds in width to a 60 degree section of the shank. Anoptional retention groove 4 is arranged towards the outer end of themounting portion.

FIGS. 6A and 6B show a sixth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section,with gear teeth 6″ arranged along at least a substantial portion of themounting portion. The gear teeth are arranged to cooperate with specialtool holders having a correspondingly shaped hole, for enhanced torquetransfer between holder and tool. The shank has one flat surface 5,which corresponds in width to a 60 degree section of the shank. Anoptional retention groove 4 is arranged towards the. outer end of themounting portion.

FIGS. 7A and 7B show a seventh embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section 7,with bevelled gear teeth 6′″ arranged at the proximal end of themounting portion. The bevelled gear teeth are arranged to cooperate withspecial tool holders having a correspondingly shaped hole, for enhancedtorque transfer between holder and tool. The shank has one flat surface5, which corresponds in width to a 60 degree section of the shank. Anoptional retention groove 4 is arranged towards the outer end of themounting portion.

FIGS. 8A to 8D show an eighth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section 7.The shank has two flat surfaces 5, which correspond in width to a 60degree section of the shank. Each flat surface has a protruding wing 9arranged on it, substantially in the middle of the flat surface andrunning longitudinally along at least a portion of the mounting portion3. The wings are arranged to cooperate with special tool holders havinga correspondingly shaped hole, for enhanced torque transfer betweenholder and tool. An optional retention groove 4 is arranged towards theouter end of the mounting portion, and is either arranged only on theflat surfaces 5 (as shown in FIG. 8B) or around the entire circumferenceof the shank (as shown in FIG. 8D).

FIGS. 9A and 9B show a ninth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally circular in cross-section 7along a major portion of the shank, with flat surfaces 5 arranged atonly the proximal end of the mounting portion. The flat surfaces arearranged to cooperate with special tool holders having a correspondinglyshaped hole, for enhanced torque transfer between holder and tool. Theflat surfaces 5 correspond in width to a 60 degree section of the shank.An optional retention groove 4 is arranged towards the outer end of themounting portion.

FIGS. 10A and 10B show a holder 10, which accepts tools having shanks aspreviously described in FIGS. 1A to 9B. The invention in its broadestaspect is in no way limited to this particular holder, or to anyspecific holder. The holder comprises an elongate connector means 15 andan outer sleeve 14, the sleeve and the parts it operates constitutingmanually operable engagement means for locking the tool in place. Thesleeve preferably has a grip-enhancing cover 17. The connector means isattachable to a power tool or hand tool (not shown) via a tool mount 11.The connector means 15 has a longitudinal hole 12, which has across-section corresponding to the cross-section of the mounting portionof the tool. Thus, depending upon the embodiment of tool for which theholder is to be used, the longitudinal hole has at least one flatsurface 13, the width of which corresponds to a 60 degree segment of thetotal hole cross-section. Two flat surfaces are shown in FIG. 10B,making the holder suitable for tools according to the second and thirdembodiments as described earlier. The part of the longitudinal holewhich is not a flat surface is substantially circular in cross-section,to accommodate tools having a hex cross-section and tools similar to theearlier described fourth, fifth, sixth and seventh embodiments, buthaving two opposite flat surfaces arranged on the shank. The torquetransfer between the holder and the tool is performed essentially by thecontacting flat surfaces of the holder and the tool, respectively. Theconnector means includes at least one radial hole 22, which cooperateswith a substantially spherical locking ball 21 movably arranged in theradial hole and which is prevented from fully entering the longitudinalhole 12 by a smaller diameter part 26 (bevelled end) of the radial hole22. The locking ball cooperates with the circumferential groove 4 (asshown in FIGS. 1A to 9B) in the tool to lock the tool in place when thetool is fully inserted into the holder 10. The outer sleeve 14 isarranged to reciprocally slide over the connector means 15 between twoend positions, and has a stepped inside diameter, having a smallerdiameter part facing the tool mount 11 and a larger diameter part 25facing the tool bit. A beveled transition 26 is arranged between the twodifferent diameter parts. The bevelled transition is arranged tocooperate with at least one transition ball 23, which will be describedin detail later. A sleeve biasing means 16, for example a coil spring,is arranged to bias the sleeve 14 away from the tool mount 11. Thetransition ball 23 is arranged in a transition hole 24 in the connectormeans 15. The transition hole is substantially radial, and preferablyangled so that the bottom of the transition hole is arranged furtherfrom the tool mount 11 than the top of the transition hole.Alternatively, the transition hole is substantially perpendicular to thelongitudinal hole 12. Thus, the transition ball 23, which has a diametersubstantially corresponding to the diameter of the transition hole 24,is slidable between a first position at the bottom of the transitionhole, to a second position protruding from the top of the transitionhole. The beveled transition 26 is pressed against the transition ball23 by the sleeve biasing means 16.

In FIG. 11A, a tool 1 is held in position to be inserted into the holder10. The locking ball 21 is free to slide in the radial hole 22, becausethe larger diameter part 25 of the sleeve 14 is located adjacent thelocking ball. The sleeve biasing means 16 is pressing the sleeve and thebeveled transition 26 against the transition ball 23, which is thusforced to the bottom of the transition hole. The sleeve is held in thisposition by a mechanism comprising a locking cavity 20, which cooperateswith a locking ring 19 arranged in a locking ring groove 18 arranged onthe elongate connector means 15, to limit the stroke of the slidingmovement of the sleeve along the elongate connector means in thedirection towards the tool mount by the locking ring blocking furthermovement because the locking ring contacts the edge of the lockingcavity (as shown in FIG. 11B), and in the direction towards the tool bythe beveled transition 26 contacting the transition ball 23 in itsposition at the bottom of the transition hole, which protrudes enough toblock the movement of the sleeve 14 when the bevelled transitioncontacts the larger diameter portion of the elongate connector means(see FIG. 11A). In the latter position, the sleeve is prevented fromsliding towards the tool mount, under the biasing influence of thebiasing means 16, by the frictional forces present between the inside ofthe sleeve and the locking ring 19.

As is shown in FIG. 11B, the tool 1 is inserted into the longitudinalhole 12. The inserted end of the tool will push the transition ball 23radially outwards in the transition hole 24. The transition ball ispressed by the inserted end of the tool bit, from its position at thebottom of the transition hole towards the sleeve and the beveledtransition 26, thus pressing the sleeve towards the tool mount. Alocking portion 27 of the sleeve 14 effectively blocks the locking ball21 from movement in the first radial hole 22, locking the tool 1 in thelongitudinal hole 12.

To release the locking ball 21, the sleeve 14 is pressed towards thetool 1, starting to release the locking ball by sliding the lockingportion 27 of the sleeve forwards. The beveled transition 26 will pushthe transition ball 23 towards the tool bit, to thereby start pushingthe tool bit out of the longitudinal hole 12. The locking portion of thesleeve fully clears the locking ball, allowing the locking ball to slideup in the first radial hole 22 sufficiently to not protrude into thelongitudinal hole 12. This allows the tool 1 to be fully removed fromthe longitudinal hole. The transition ball 23 is seated in the firstposition in the transition hole 24, blocking any further movement of thesleeve 14 in the direction towards the tool insertion hole (longitudinalhole). As soon as the tool has left the longitudinal hole, the lockingball can enter the longitudinal hole and thus release the sleeve 14 forsliding towards the tool mount 11, but the sleeve is prevented fromsliding by the frictional forces between the sleeve and the lockingring, as described above. Thus, when inserting a tool bit into theholder, these frictional forces will have to be overcome by the userpushing the tool bit into the holder with a sufficient force to releasethe sleeve.

FIGS. 12A to 12C show the holder 10 according to the invention used witha standard size drill bit 100 having a hex mounting portion 101. Alltechnical features of the holder are the same as earlier described andhave the same reference numerals. The hex cross-section of the drill bitfits without problems in the longitudinal hole 12 of the holder, withthe two flat surfaces 13 making contact with two opposite surfaces ofthe hex mounting portion and the corners between the remaining four hexflat surfaces making contact with the longitudinal hole's substantiallycircular surface. The mounting portion of the drill bit and its mountinggroove 102 (corresponding to the groove 4 of the earlier describedtools) interacts with the locking ball 21 and the transition ball 23 ofthe holder as has been described for FIGS. 10A and 10B. Thus, the holderaccording to the invention can be used together with either the earlierdescribed tools or a standard size hex mounting portion drill bit.

FIGS. 13A to 13C show the holder 10 according to the invention used witha standard size screw bit 200 having a hex mounting portion 201 and amounting groove 202. All technical features of the holder are the sameas earlier described and have the same reference numerals. The hexcross-section of the drill bit fits without problems in the longitudinalhole 12 of the holder, with the two flat surfaces 13 making contact withtwo opposite surfaces of the hex mounting portion and the cornersbetween the remaining four hex flat surfaces making contact with thelongitudinal hole's substantially circular surface. The mounting portionof the drill bit and its mounting groove 202 (corresponding to thegroove 4 of the earlier described tools) interacts with the locking ball21 and the transition ball 23 of the holder as has been described forFIGS. 10A and 10B. Thus, the holder according to the invention can beused together with either the earlier described tools or a standard sizehex mounting portion screw bit.

FIG. 14 shows in detail a further embodiment of a mounting portion 3 ofa shank 2 of a tool 1 according to the invention. The groove 4 isarranged only on those portions of the shank which do not have the flatportions 5. Alternatively and as shown in FIG. 15, the mounting portion3 of a shank 2 of a tool 1 according to the invention has a groove 4arranged only on those portions of the shank which have the flatportions 5.

FIGS. 16A and 16B show a tenth embodiment of a mounting portion 3 of ashank 2 of a tool 1. The shank is generally square in cross-sectionalong a major portion of the shank, with flat surfaces 5. The cornersmay be rounded or sharp. The flat surfaces are arranged to cooperatewith special tool holders having a correspondingly shaped hole, forenhanced torque transfer between holder and tool. The flat surfaces 5may correspond in width to a 60 degree section of the shank. An optionalretention groove 4 is arranged towards the outer end of the mountingportion.

FIGS. 17A and 17B show an eleventh embodiment of a mounting portion 3 ofa shank 2 of a tool 1. The shank is generally triangular incross-section along a major portion of the shank, with flat surfaces 5with sharp or rounded corners. The flat surfaces are arranged tocooperate with special tool holders having a correspondingly shapedhole, for enhanced torque transfer between holder and tool. The flatsurfaces. 5 may correspond in width to a 60 degree section of the shank.An optional retention groove 4 is arranged towards the outer end of themounting portion.

FIGS. 18A and 18B show an eleventh embodiment of a mounting portion 3 ofa shank 2 of a tool 1. The shank is generally triangular incross-section along a major portion of the shank, with outwardly curvedsurfaces 7. The curved surfaces are arranged to cooperate with specialtool holders having a correspondingly shaped, for enhanced torquetransfer between holder and tool. An optional retention groove 4 isarranged towards the outer end of the mounting portion.

A twelfth embodiment of a mounting portion 3 of a shank 2 of a tool 1 isshown in FIGS. 19A and 19B. This embodiment is similar to the thirdembodiment shown in FIGS. 3A and 3B. The shank is generally rectangularin cross-section, having two first flat portions 5 arranged oppositeeach other on the shank and two second generally flat portions 5′connecting the first flat portions. Each first flat portion 5corresponds in width to a 60 degree section of the shank. An optionalretention groove 4 is arranged towards the outer end of the mountingportion.

The tools as described, when applied to a drill bit, have a number ofapparent advantages over the prior art known as two-piece drill bits.The two-piece construction has an ordinary substantially circularcross-section drill mounted in a longitudinal hole in a hexcross-section mounting piece.

The combination of a tool and holder according to any of the describedembodiments of the invention adds safety to the use of the device,because the device automatically locks the tool bit in the holder afterinsertion. No action, other than the insertion itself, has to beperformed by the user to insert and lock the tool bit in place. As asafeguard, the device has to be actively manipulated in order to releasethe tool bit from the holder again, but the tool bit will beautomatically dislodged during this manipulation, so that the tool bitcan be removed from the holder using only one hand.

It will be appreciated that the above description relates to thepreferred embodiments by way of example only. Many variations on theinvention will be obvious to those knowledgeable in the field, and suchobvious variations are within the scope of the invention as describedand claimed, whether or not expressly described. For example, irregular,i.e. non-symmetrical, cross-sections may be used for both the shank andthe holder mounting hole. An L-shape or a triangular shape might beused, where at least one of the flat sides correspond to the flat of astandard hex bit/holder. Naturally, and this applies to all embodimentsof the invention, the at least one flat side of the shank used fortorque transfer may be substantially narrower than the correspondingflat of the holder mounting hole. The basic requirement of theshank/holder fit is that only a certain amount of lateral movement ofthe shank inside the holder is allowed, to accurately hold the toolduring operation.

In the preceding description and in the accompanying claims, it isintended that expressions such as “generally triangular” or “generallyrectangular” or “generally square” should mean that the shapes areessentially so, but may have somewhat rounded surfaces, corners and/oredges, which still suggesting the overall shape.

INDUSTRIAL APPLICABILITY

The invention provides tools having novel shanks for easy and securemounting in tool holders.

1. For use in a tool holder having an aperture with a cross-sectionalshape having at least one non-circular 60-degree segment, a tool havinga distal operative portion and a proximal shank with a mounting portionfor mounting said tool in said aperture of said tool holder, saidmounting portion comprising at least one cross section includingcircular and non-circular portions, said non-circular portion having atleast one 60-degree segment configured for engagement in said aperturewith said non-circular 60-degree segment of said aperture and whereineach circular portion has a common centre of axis with the tool; whereinthere are two said 60-degree segments, each having a flat surface, saidtwo segments being on opposite sides of said mounting portions from eachother.
 2. A tool as recited in claim 1, wherein a portion of saidmounting portion has a circumferential groove extending at least partwayaround the mounting portion, adapted to receive locking means of saidholder.
 3. A tool as recited in claim 1, wherein a portion of saidmounting portion has a circumferential groove extending at least partwayaround the mounting portion, adapted to receive locking means of saidholder.
 4. A combination of a tool and a tool driver having a holderwith a distal axial aperture for receiving said tool, said tool having adistal operative portion and a proximal shank with a mounting portionfor mounting said tool in said holder, said mounting portion comprisingat least one cross section including circular and non-circular portions,said non-circular portion having at least one 60-degree segmentconfigured for engagement in said aperture with a non-circular 60-degreesegment of said aperture and wherein each circular portion has a commoncentre of axis with the tool, said aperture having a cross-sectionalshape having a 60-degree segment for each of said 60-degree segments ofsaid mounting portion, shaped correspondingly to each said non-circularsegment of said mounting portion wherein there are two said 60-degreesegments, each having a flat surface, said two segments being onopposite sides of said mounting portions from each other; wherein saidmounting portion has two said 60-degree segments having segment endsjoined by a flat surface, said two segments being on opposite sides ofsaid mounting portion from each other.
 5. A combination as recited inclaim 4, further comprising locking means for locking said tool in saidholder.
 6. A combination as recited in claim 5, wherein said lockingmeans comprises manually operated engagement means for locking saidmounting portion in said holder.
 7. A combination as recited in claim 5,wherein said locking means comprises engagement means whichautomatically lock said mounting portion in said holder, upon insertionof a tool in said holder.
 8. A combination as recited in claim 5,wherein said locking means comprises a locking ball mechanism.